Rheumatoid arthritis (RA) is a chronic disease characterized by synovial inflammation, synovial fibroblast proliferation, transformation, and ultimately invasion into adjacent cartilage resulting in pannus formation and joint destruction. Mucins (MUCs) are a family of heavily O-glycosylated glycoproteins that are over-expressed in many cancers and inflammatory diseases. MUCs are known to function as cell adhesion molecules and in the protection of epithelial membranes, but additional functional roles for MUCs are likely undetermined. Preliminary data examining the expression of mucins in RA and osteoarthritis (OA) indicate that: 1) MUC3 and MUC5AC expression is upregulated in arthritic synovial tissue over normal synovial tissue; 2) synovial fibroblasts express MUC3 in culture, which can be enhanced by cytokine stimulation, and 3) MUC3 plays a novel functional role inducing the migration of RA synovial fibroblasts. This application will confirm and build upon these preliminary results through a more detailed examination of the expression and functions of MUC3 and MUC5AC in arthritis. From these preliminary results it is hypothesized that MUC3 and MUC5AC are expressed in human and rat arthritic synovium under the control of inflammatory cytokines, and function as migratory, adhesive, and/or apoptotic factors on synovial fibroblasts. Aim 1 of this application is to determine the expression of MUC3 and MUC5AC in arthritic and control synovium under conventional and stimulated conditions using RT-PCR to study MUC gene expression and ELISA, flow cytometry, and Western blotting to determine soluble, cell surface bound, and total MUC protein production. Aim 2 of this application, looks to characterize the temporal expression of MUC3 and MUC5AC in rat adjuvant-induced arthritis (AIA). Again, RT-PCR will be employed to determine MUC gene expression and ELISA and immunohistochemistry will be used to determine MUC protein production. The cell types responsible for expression of MUC3 and MUC5AC will be determined using double fluorescent immunostaining techniques and the total MUC3 and MUC5AC expression will be correlated to clinical inflammatory measurements throughout the progression of rat AIA. Aim 3 of this application seeks to determine whether MUC3 and MUC5AC function in the arthritic joint as migratory, adhesion and/or apoptotic factors. Specifically, synovial fibroblast chemotaxis assays will be used to determine if immunodepletion of MUC3 and MUC5AC can alter cell migration. Finally, siRNA will be used to lower MUC3 expression in synovial fibroblasts while the level of apoptosis and leukocyte adhesion are evaluated. [unreadable] [unreadable] PUBLIC HEALTH REVELANCE. Rheumatoid arthritis (RA) and osteoarthritis (OA) are common arthritic diseases affecting as much as 1 percent and 12.1 percent of adults in the United States of America respectively. This application will expand our understanding of a recent finding that mucins, MUC3 and MUC5AC, are elevated in synovial tissues of patients with RA and OA. Specifically, this application will better characterize the production of MUC3 and MUC5AC in human RA and OA joints, it will determine the timing of mucin expression in a rat model of RA, and it will identify functions for mucins in the development of arthritic diseases. [unreadable] [unreadable] [unreadable]